The present invention relates to a new and improved rotary nozzle system for metallurgical vessels, especially steel casting ladles.
Generally speaking, the rotary nozzle system for metallurgical vessels, is of the type comprising a stationary closure portion or part containing a refractory bottom plate and a closure portion or part which is rotatable relative to the stationary closure portion. The rotatable closure portion contains a rotatable toothed rim mounted at the stationary closure portion and a refractory slide plate which resiliently bears against the bottom plate.
With heretofore known rotary nozzle systems of this type, for intance as disclosed in German patent publication No. 2,404,881 or U.S. Pat. No. 3,511,471, a metallic support plate, which receives the refractory slide plate, is supported at its periphery at a stationary bearing or mounting ring. The bearing ring is secured, in turn, by means of springs at a base plate. These springs transmit the contact force for the slide plate, by means of the bearing ring, to the support plate. The rotary drive--in one case, accomplished by means of a gearing drive and, in the other case, by means of an insertable hand lever--thus engages directly at the support plate. Exchange of the refractory closure elements or parts, especially the bottom plate and the slide plate, which must be replaced after a few pours or teeming operations to ensure for proper operation, is cumbersome with these prior art rotary slide systems and cannot satisfy the high operational security which is demanded. In order to render the aforementioned refractory elements or parts accessible, it is necessary to dismantle, each time along with the support plate, also the bearing ring and its holding springs and to interrupt the mechanical rotary drive. Upon renewed assembly there particularly exists the difficulty of again adjusting, through the tensioning of the springs, the uniform surface compression between the slide plate and the bottom plate which is needed for achieving a positive sealing action, since the spring forces which engage the bearing ring far outside of the edges of the plates, produce considerable tilting moments at the sealing surfaces and excessive, locally differing edge compression. Moreover, the direct rotatable mounting of the support plate is incompatible with the intensive and considerably varying thermal load of such support plate which is caused by the molten metal.
According to a further state-of-the-art rotary nozzle system, as disclosed in Austrian Pat. No. 322,753, there is formed a spherical sealing surface between a concave, refractory bottom portion and a sleeve-shaped refractory slide element or part having a convex top surface. The slide element or part is mounted for corotation in a central opening of a metallic disc, which is threadably connected at the outer periphery with the rotatable toothed rim and is constructed as a plate spring. This plate spring therefore must transmit the drive moment to the slide element and at the same time apply the contact pressure. By virtue of the combined effects of the material wear or loading and the high temperatures to which such metal spring is exposed, there is however rendered quite questionable whether there can be achieved a positive interconnection of the elements forming the rotary nozzle system so as to ensure for the requisite sealing action. Even upon tightening the attachment or fastening screws it is not possible to determine the stressed state of the plate spring, and with this prior art arrangement there cannot be accomplished reliable centering and guiding of the slide element.